absolute
value
The absolute value of a number is the distance that number is from zero.
The absolute value of a positive number or zero is that number.
The absolute value of a negative number is the opposite of that number,
and the absolute value of zero is zero which is neither positive
or negative.

Ex:
|3| = 3, and |-3| = 3, |0| = 0 .
Both 3 and -3 are 3 jumps away from zero, so they have the same absolute
value of 3.

The absolute value bars | |,
act as grouping symbols. You must simplify any expressions within these
bars before finding the final absolute value.

Ex: |3-7| = |-4| =
4.

acre
A unit of area often used to measure plots of land. One acre is equivalent
to exactly 43,560 square feet, or 4,840 square yards, or 1/640 of a square
mile, or about 4,047 square meters.

acute
angle
An angle whose measure is between 0° and 90º. We like to think of them
as the "cute" skinny angles.

addend
A number to be added.

Addition
Property of Equality
If a = b, then a + c= b + c. Add the same
thing to both sides of an equation and you still have an equation.

Ex:
3 = 12/4
7 + 3 = 12/4 + 7
10 = 10

additive
identity The number
zero. When you add zero to any number, you do not change its identity,
thus the name, additive identity.

Additive
Identity Property of Zero For any number n:
n + 0 = n. If you add zero to any other number, you do not change
its identity.

Additive
InverseThe number,
which when added to a number, gives a sum of 0. The additive inverse of
n is denoted -n. Also called opposite.

Add-opp
Property of Subtraction For any numbers
a and b: a - b = a + -b. In words, subtracting
b is the same as adding the opposite of b.

adjacent
angles
Two nonstraight and nonzero angles with a common side interior to the
angle formed by the noncommon sides.

adjacent
sides
In a polygon, two sides with an endpoint in common.

adjacent
vertices
In a polygon, endpoints of a side.

algebraic
expression
An expression that contains a variable alone or with numbers and operation
symbols.

Ex:
y
3xy
4x + 2

algorithm
A sequence of steps that leads to a desired result.

alternate
exterior angles
Angles formed by two lines and a transversal whose interiors are not
between the two lines and are on different sides of the transversal.

Angles one and seven
are alternate exterior angles as are angles two and eight.

When the two lines cut
by the transversal are parallel, the alternate exterior angles will
be congruent.

alternate
interior angles
Angles formed by two lines cut by a transversal. They are between
the two lines and on alternate sides of the transversal.

Angles three and five
are alternate interior angles as are angles four and six.

When the two lines cut
by the transversal are parallel, the alternate interior angles will
be congruent.

altitude
In a triangle or trapezoid, the segment from a vertex perpendicular to
the line containing the opposite side;
also, the length of that segment. In a prism or cylinder, the distance
between the bases. In a pyramid or cone, the length of a segment from
the vertex perpendicular to the plane of the base. Also called height.

altitude
of a triangle
The perpendicular distance from any vertex of a triangle to the side opposite
that vertex. Also called height.

analytic
geometry
A geometry in which points are represented by coordinates and where algebraic
methods of reasoning are utilized.

angle
The union of two rays with the same endpoint.
The rays are the sides and the common endpoint is called the vertex. There
are many types of angles. See the definitions for zero angle, right angle,
straight angle, acute angle, obtuse angle, reflex angle.

angle bisector
The ray with points in the interior of an angle that forms two angles
of equal measure with the sides of the angle.

angle of
depression
An angle measured from the horizontal plane downward from an observer's
eye to a given point below the plane.

angle of
elevation
An angle measured from the horizontal plane upward from an observer's
eye to a given point above the plane.

angle of
inclination
See angle of elevation.

antecedent
The "if" clause of a conditional. Also called hypothesis.

apothem
The perpendicular segment from the center of a regular n-gon to one of
its sides.

arc
A path from one point (node) of a network to another point (its endpoints
or vertices).

A part of a circle connecting two points (its endpoints) on the circle.

area
Measure of the space inside a two-dimensional figure. Area is measured
in square units.

Area
Model for Multiplication
The area of a rectangle with length l and width w is
l times w or a = lw.

arthmetic
mean
The result of adding the n numbers in a data set and dividing the
sum by n. Also called the average or mean.

Associative
Property of AdditionFor
any numbers a, b, and c:
( a + b)+ c = a + ( b + c ) = a + b + c. The positions
of the numbers do not change, the placement of the grouping symbols changes.

Ex:(1+2)+3 = 1+(2+3)
3+3 = 1+56=6

Associative
Property of Multiplication
For any numbers a, b, and c:
a( bc ) = ( ab )c = abc. The positions of the numbers do not change,
the placement of the grouping symbols changes.

Ex:
3(4x5) = (3x4)5
3(20) = 12(5)60 = 60

automatic
drawer
Computer software or calculator that enables geometric figures to be constructed
from input by the user. Click HERE
to get one we recommend.

auxiliary
figure
A figure that is added to a given figure, often to aid in completing proofs.

averageA number representing
a set of other numbers determined by taking the sum of those numbers and
dividing by the number of them. Also called mean orarithmetic
mean.

axis
A line of reference in a coordinate system. Plural: axes.

axis of
a cone
The line through the cone's vertex and the center of its base.